- 學位論文
鉑改質奈米鈦管光催化甲醇水溶液之產氫研究
Hydrogen Production from Methanol Solution by Pt doping TNTs under Light Irradiation
摘要
工業革命後，人類對於能源的需求大增，但台灣本土的自然資源有限，再加上主要能源－化石燃料燃燒後所排放的二氧化碳、氮氧化物、硫氧化物會污染環境，造成溫室效應等問題，因此替代能源逐漸受到重視。氫能源被認為是最具潛力的替代能源，其能量密度高達120 MJ/kg，且可由水製備而得，燃燒後又回到水，符合環保，然而自然界中氫氣大多是以化合物的形式存在，因此現階段最重要的是如何以符合經濟效益的方式來量產氫氣。 近年來，有不少研究以二氧化鈦光觸媒利用太陽光來分解水產生氫氣，二氧化鈦因具有物化性質穩定、耐酸鹼、照光後不發生光腐蝕、便宜、無毒等優勢，是目前最廣泛使用的光觸媒。但二氧化鈦為紫外光觸媒，無法有效利用太陽光譜中的可見光，且其受光激發所產生的電子電洞容易在其內部或表面再結合等因素，均會降低水轉換成氫氣的效率。 為提升產氫效率，本研究利用光沉積法將Pt金屬批覆於二氧化鈦及比表面積較大的奈米鈦管(TNTs)上，並以紫外光 ( 250W, 320-400 nm ) 和可見光 ( 150W, 400-700 nm ) 燈管光催化甲醇水溶液產生氫氣，以期能提供無污染、無害的清潔能源。在實驗過程中，甲醇濃度和觸媒劑量均是影響產氫效率的重要參數，本研究最佳觸媒劑量比例是以0.25 g TiO2置於20 vol%、500mL甲醇水溶液中反應，產氫效率為491.3 μmol•h-1。 實驗結果顯示不論是在紫外光還是可見光的照射下，1 wt%Pt/TNTs均具有最高的產氫效率，分別為2331 μmol•h-1 和137.7 μmol•h-1 ，純TiO2或TNTs皆無法於可見光下反應產氫，經過Pt改質後之光觸媒確實有將吸收光譜移至可見光區的作用，同時也利用金屬對電子的強烈吸引力，能有效抑制電子與電洞再結合，增加水解產氫的機率。
並列摘要
Hydrogen gas has been one of the most promising renewable energy nowadays and the final product of hydrogen combustion is nothing but water. However, hydrogen gas does not occur naturally in large quantities on earth but separated from other compounds. Therefore, many researches have been conducted to produce hydrogen from water by using photocatalysts. Compared with other photocatalysts, TiO2 is much more promising photocatalysts material as it is stable, non-corrosive, environmentally friendly, nontoxic and cost effective. Presently, the energy conversion efficiency from solar to hydrogen by TiO2 photocatalytic water-splitting is still low, mainly due to the following reasons: inability to utilize visible light, fast backward reaction and the recombination of photo-generated electron/hole pairs. In order to enhance the photocatalytic efficiency in water-splitting reactions under ultraviolet ( UV ) irradiation, tremendous efforts focused on the influence of addition of sacrificial reagents such as methanol, Na2S, I- and IO3- ions, were used to obtain an effective water-splitting to H and O atoms. Some researchers studied the modification of TiO2 by means of the preparation of titanate nanotubes ( TNTs ) to increase the specific surface area, doping metals ( like Pt, Pd, Au, Cu and so on ) onto the photocatalysts in order to increase its usage and hydrogen generation efficiency. Therefore, this study investigated the photocatalytic conversion of methanol solution to H2 under ultraviolet light irradiation ( 250W, 320-400 nm ) and visible light ( 150W, 400-700 nm ) over Pt/TiO2 and Pt/TNTs which is prepared by photodeposition method. The optimum photocatalyst dose and concentration of methanol solution were also investigated. The results showed that the hydrogen production is the highest with 20 vol% methanol solution over 0.25 g TiO2, which achieved 491.3 μmol•h-1. Moreover, doping metal onto the photocatalysts could further promote the hydrogen production. In this study, doped Pt onto TiO2 and TNTs is in order to reduce the recombination of electrons and holes. The results showed that the best photocatalyst is 1 wt%Pt/TNTs, which hydrogen production achieved 2331 μmol•h-1 under UV light and 137.7 μmol•h-1 under visible light with 20 vol% methanol solution.
並列關鍵字
Hydrogen ； Methanol solution ； Photocatalyst ； Platinum ； Titanium dioxide ； Titanium nanotubes參考文獻
延伸閱讀
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